I used to think so, but not any more:
We assess whether there is a strong causal relationship
between congressional districting and polarization. We find very little
evidence for such a link. First, we show that congressional
polarization is primarily a function of the differences in how
Democrats and Republicans represent the same districts rather than a
function of which districts each party represents or the distribution
of constituency preferences. Second, we conduct simulations to gauge
the level of polarization under various “neutral” districting
procedures. We find that the actual levels of polarization are not much
higher than those produced by the simulations. We do find that
gerrymandering has increased the Republican seat share in the House;
however, this increase is not an important source of polarization.
So what does cause voter polarization? Here is a counterintuitive hypothesis: political extremists are most active when they fear that the extremists from the other side might win. Each candidate requires those extremists for support and resources, and when a candidate wins he or she then must polarize to some extent. If you think of the extremists as motivated by fear of the other side, in a lopsided district they are more likely to stay at home and keep their mouths shut, thereby allowing the candidate to straddle the center. It’s a close race that brings out the partisans and gives them some measure of ex post control.
Might this be true?
We examine DW-Nominate scores for members of the House of Representatives who served from 1993 through 2000. The most politically extreme members tended to represent politically competitive districts, a result at odds with traditional Downsian expectations.
File this one under "I’m still fundamentally confused."